U.S. Pat. Nos. 4,880,076 and 5,002,151 both disclose hearing aids that are modified in various ways to accept complementary user-disposable foam sleeve adapted to mount on and fit around a distal end portion of the hearing aid to seal it to the user's ear canal. Although technically feasible, all of these combinations have thus far proved commercially unappealing, both because of their technical complexity and their relatively high cost. U.S. Pat. No. 5,682,020 describes another way of sealing a hearing aid to a user's ear canal, viz., by removably adhering a foam layer to the otherwise canal-contacting periphery of the hearing aid. Although this technique is quite effective, the process of adhering the foam to the proper location requires a degree of manual dexterity sometimes lacking in persons who wear hearing aids. Yet another prior art technique involves permanently adhering a foam ring to the hearing aid, thereby preventing the user from removing and replacing it. In the absence of adhesive, such a ring is likely to slide off and remain in the ear canal when the hearing aid is removed.
Guards for the ends of sound delivery tubes inserted in the ear canal that restrict cerumen from entering those tubes are commercially available. Known cerumen guards of this type are moldings of stiff polymeric material that releasably engage a knob-like end part at the end of the sound delivery tube, and provide passageways through the guard sized and oriented to provide that cerumen restricting function.